Low-temperature densification mechanism and properties of h-BN@SiC/ZrO2 composite ceramics prepared by hot-pressing

High-density h-BN@SiC/ZrO 2 composites with different ZrO 2 contents were prepared by hot-pressing. The microstructure, flexural strength, thermal shock behavior, thermal expansion properties and corrosion resistance of the composites in molten steel were systematically investigated. The construction of the h-BN@SiC core-shell structure is conducive to the formation of a uniform and continuous network structure during the sintering process. This significantly improves the sintering performance of h-BN-based materials and enables the low-temperature preparation of high-density products. Moreover, the uniform distribution of SiC can effectively coordinate the thermal matching between h-BN and ZrO 2 , significantly improving the high-temperature performance of the material. During the corrosion process, the SiC network structure can effectively bind ZrO 2 and BN particles, effectively resist the erosion of high-temperature molten steel, and its erosion resistance increases with the increase of ZrO 2 content. Especially, when the ZrO 2 content reached 40%, the erosion depth of the sample was merely 160.61 μm after being immersed in static molten steel for 120 min. Moreover, the h-BN@SiC/ZrO 2 composite with 30 wt% ZrO 2 demonstrates superior comprehensive performance: It achieves a flexural strength of 159.63 MPa, retains 87.08% of its original strength after thermal shock testing, exhibits a low apparent porosity of 3.37%, and possesses an average coefficient of thermal expansion as low as 3.95 × 10 −6 /K −1 . The comprehensive properties of h-BN@SiC/ZrO 2 composites were obviously improved by SiC network structure.